This invention relates to mechanical spring seals of the type in which a deformable seal element, typically of synthetic material, is spring loaded by an internal metal spring element, and is particularly directed to mechanical spring seals of the above type of simple cross-sectional shape and having good resiliency, and in which the spring element is readily inserted and locked into the seal element.
Spring seals in a wide range of sizes are increasingly being used for a range of critical applications as static and dynamic sealing elements. They are far superior to O-rings where pressure and temperature requirements are substantial, for example, because they provide long wear with low friction when interposed between opposing surfaces, while being resistant to the high temperature levels and pressures that may be encountered.
The spring seals are based upon the concept of using an outer cover or jacket of stable high temperature resistant resin, such as Nylon or Teflon, which jacket contacts the opposing surfaces to be sealed, while incorporating, in a cavity in the jacket, an elongated spring element, typically of metal. Although synthetic resin sealing materials are inert, slippery and withstand wear, they have little shape memory. The metal spring compensates for the lack of shape memory and resiliency of the jacket materials by urging the sides of the cover outwardly against the facing surfaces.
A number of different configurations of spring seals are known, as for example my prior U.S. Pat. No. 4,133,542, on a configuration of, and method for making, a spring seal. In this structure the spring has a base that is circular in form, for insertion into a mating concavity in the jacket. It is superior in a number of respects to prior U-shaped spring seal configurations, because the U-shaped elements have sharp corners creating stress points when the sides are compressed. Also, tips on the jacket are required to hold in the spring and these can be readily damaged or broken off to allow loss or partial displacement of the spring relative to the jacket, with consequent adverse effects on sealing properties. Similarly, where square type or rectangular type spring elements are employed, the sharp corners are unduly stressed since all the bending occurs at the corners, and such corners tend to snap or become fatigued.
A number of configurations are known in which the spring is circular in shape, but the circular spring shape provides very little resilience. In consequence, the product manufacturer who is to use the seal is required to manufacture a part in which separated but facing surfaces have very precise spacing tolerances, substantially increasing his costs. A concomitant factor is that, because of the limited resilience, static seals that fit a given spacing must be of different size than dynamic seals used for the same spacing.
The special shape of my above patent minimizes some of these problems, but on the other hand is a somewhat more complex configuration that requires a special jacket shape. Further, none of the spring seals previously known permits incorporation of an internal O-ring, which is sometimes desirable in practical applications, as a substitute for the metal spring. Also, many spring seals require a different configuration for a static application as opposed to a dynamic application.
It is accordingly desirable to provide a mechanical spring seal having a deformable seal element or jacket, and a cooperating spring element which fits within the jacket, wherein the cross sectional shapes of the mating surfaces of the jacket and spring element are non-complex. The spring element should be easily insertable within the jacket, while locking the spring in position within the jacket. In addition, it is also desirable that the spring element of such mechanical seal be free of sharp angles or turns to avoid stress and fatigue points. Still another aim of the invention is the provision of a seal element of the above type, which has good resilience, is highly durable, and which is effective for both static and dynamic applications.